The present invention relates in general to firearms, and more particularly to a hypodermic dart gun for use in anesthetizing wild animals undergoing zoological study and the like.
U.S. Pat. No. 3,381,403 to Murdock discloses a hypodermic dart gun of the firearm type wherein combustion gases generated by an exploding blank cartridge are fed into the breech end of a gun barrel to forcibly eject a hypodermic dart contained therein. In one embodiment, Murdock varies the volume of a relatively large combustion gas expansion chamber to regulate the ejection velocity of the dart, and hence its range. In another Murdock embodiment, combustion gases from a relatively large fixed volume expansion chamber are fed into the breech end of the gun barrel via an adjustable valve regulating the feed rate of the combustion gases, and hence determining the velocity and effective range of the ejected dart.
While the Murdock gun may provide adequate regulation of dart velocity and range, it is of complex design, requiring the generated combustion gases from an exploded blank cartridge to follow a sinuous route before finally being injected into the breech end of the barrel. Such sinuous routing of the combustion gases through one or more relatively large volume gas expansion chambers may result in incomplete burning of the blank cartridge gunpowder, wherein the ejection velocity of the dart could be deleteriously affected. Also, the incompletely burned gunpowder residue could clog the combustion gas pathway after only a few firings of the gun. The complexity of the Murdock gun makes it very difficult to clean. Further, manipulation of a movable gun barrel is required to load a dart into the one version of Murdock's gun, while removal of a barrel end cap is required to load another Murdock version of his gun. Such dart loading techniques are considered undesirable from both a complexity and time-consuming standpoint.
In view of the foregoing disadvantages of the prior art Murdock device, it would be desirable to provide a firearm type dart gun of simpler design having means for adjusting the ejection velocity of the associated hypodermic dart. Such a simplified design should ensure complete burning of conventional blank cartridge gunpowder, and should also permit rapid loading of the hypodermic dart without excessive manipulation or partial disassembly of the gun.